How the hell do you go from San Andreas to GTA4?
Phone calls to go bowling, bad checkpointing, poor mission design (and they lacked variety), weird controls, story that falls off the rails after 1/4 of the way in, poor game design structure . Niko was also a strange character, who was completely dissonant with what the character stood for and what his actions were (ie: the game's tone and the gameplay continuously clashed--get away from a life of crime, but kill tons of people). Cars didn't handle very nicely. It just ended up not being fun to play by virtue of just feeling repetitive or not fun to play. The city itself was just there to give off the illusion of scale. Couldn't talk to a lot of people, couldn't go into a lot of buildings, yet you could watch TV/go on the internet which should have really been relegated to side stuff as opposed to core gameplay mechanics. Additionally, make the relationship system worth working on or don't include it at all. The game, overall, was just boring and it felt lacking in substantial and varied content.
Also, button-mashing to sprint is a stupid decision.
At least Gay Tony and The Lost and the Damned were decent, I guess.